In industrial production, welding may involve raising, cladding, building up, filling, hard facing, overlaying, joining, and other welding applications. When confronted with a work piece having a curved surface, an orbital welding process may be used to rotate the welding head to apply a weld to the curved surface. The most common examples where orbital welding is used is the welding of pipe. Pipe welding may include thin walled application where the welding head is rotated about the outer surface between two piece ends of pipe. Alternatively, pipe welding may include deep groove geometries where the welding electrode extends into a groove formed between the two pipes being joined to lay down successive beads of weld material to fill the groove to join the thick walled pipes. Orbital welding systems may include a welding head that is mounted on a guide track or a fixture that clamps or is otherwise supported on the workpiece and rotated to supply a weld.
One parameter influencing the outcome of welding operations, including orbital welding operations, is the lead or lag angle of the welding torch. The lead or lag angle of the torch can be measured as the angle formed by a straight line from the electrode and a line perpendicular to the weld axis (or the line through the center of the weld along its length). Lead and lag angles are important because they influence the penetration of the welding torch as well as the geometry and consistency of the weld bead. A torch inclined in the direction of the orbital welder's motion is said to have a lead angle, while a torch inclined opposite the direction of the orbital welder's motion is said to have a lag angle. In other words, with a lead angle, the arc is pointed in the direction of unwelded base metal as the weld progresses. Other definitions of lead and lag are provided with reference to the electrode's leaning toward filler wire (lead) or away from filler wire (lag). Zero lead/lag angle occurs when the torch is perpendicular to the surface being welded, or a plane defined by the point being welded in nonlinear applications.
Thus, it is clearly important to control lead or lag angle to ensure proper welding in terms of structural integrity and aesthetics. Various techniques for applying lead or lag angle suffer from common drawbacks. An example of deficiencies in the art includes the inability to simply and rapidly readjust to a specific angle. While dials, linkages, and other complex apparatuses have been employed, these require adjustment to and re-setting at a desired angle with every change. In another example of shortcomings in the art, no means to accurately measure lead or lag angle or establish a repeatable reference point is provided. Welding attachments or controls employing flexible necks, probes or rollers about which the weld head automatically adjusts, or non-scaled adjusting members exhibit these deficiencies.
These complexities are multiplied when utilizing an orbital welder, as opposed to earlier or alternative welding equipment. In situations employing orbital welders and others, lead and lag angle control can be managed by an operator lacking a measurable frame of reference for repeatability. In fact, it is not uncommon for operators to attempt awkward employment of protractors when configuring the lead or lag angle of a welding torch. For example, a user manual for earlier products states explicitly: “The use of a Protractor is recommended for a precise setting of TILT and LEAD/LAG.” See, e.g., Arc Machines MODEL 77 WELD HEAD OPERATION MANUAL, Dec. 12, 2007. Even if the use of a protractor is accurate in some circumstances (a result not guaranteed), this technique is slow and requires diligent care and external means for recording earlier angles.
While burdensome during an initial setup, the inconvenience of utilizing protractors or rough estimation is compounded in situations in which a welding torch is manipulated, changing the lead or lag angle, during a welding operation. For example, the accumulation of spatter in a welding nozzle frequently necessitates the nozzle be cleaned before an operation can be completed. Both consumable and nonconsumable electrodes can experience problems requiring operator intervention to cure. Such operations may require rotation of the welding torch away from the work piece, and at times necessitate full removal of a welding torch from an orbital welding assembly. Further, some welding operations utilize varying or multiple lead or lag angles throughout a process, which can also entail challenging operator manipulation, especially when components are hot or welded portions of a work piece are still malleable.
Accordingly, orbital welding heads can be improved by integrating systems that allow for quick setting or resetting of lead or lag angle and/or accurate, repeatable measurement of lead or lag angle in varying conditions, particularly when employing orbital welders.